Custom Tunnel

print("Width = ?")
w = tonumber(read())
print("Height = ?")
h = tonumber(read())
print("Depth = ?")
d = tonumber(read())

for a=0,d-1,1 do
    turtle.dig()
    turtle.forward()
    turtle.turnRight()
    for c=0,h-2,1 do
        turtle.digUp()
        turtle.up()
    end
    for b=0,h-2,1 do
        turtle.down()
    end
    for b=0,w-2,1 do
        turtle.dig()
        turtle.forward()
        for c=0,h-2,1 do
            turtle.digUp()
            turtle.up()
        end
        for b=0,h-2,1 do
            turtle.down()
        end
    end
    for b=0,w-2,1 do
        turtle.back()
    end
    turtle.turnLeft()
end